Treatment of oil producing sands



Patented Feb. 22, 1944 UNITED STATES PATENT or ies TREATMENT OF OIL PRODUCING SANDS No Drawing. Application April 25, 1939, Serial No. 269,910

Claims. (Cl. 252-855) This invention relates 'to the production of oil from oil-producing formations and particularly to a method of increasing the effective permeability of oil-containing formations immediately surrounding a well bore hole.

In the drilling of oil and gas wells, particularly by rotary tool methods, it is conventional to employ a drilling fluid to aid the drilling operations. The drilling fluid, generally an aqueous suspension of solid matter, such as clay, bentonite or other similar material or even plain water, is circulated down through the drill stem around the tool or drill bit employed for the drilling operation and rises between the drill stem and the wall of the bore hole to the surface of the well. One purpose of the use of the drilling fluid is to carry to the surface of the bore hole the cuttings made by the drill bit. However, one of the most important functions of the drilling fluid is, by its weight and pressure, to prevent the well from blowing in prematurely. The prevention of the blowing in or the entrance into the bore hole of the high pressure fluids contained in the penetrated formations requires that the drilling fluid be at a relatively higher pressure than that contained in-the penetrated formations. In order to insure that the pressure of the drilling fluid shall be sufliciently great, it is conventional to add to the drilling fluid such weighted materials as barytes, hematite or finely divided iron when the clay content of the said fluid is not in itself sufllcient. The producing formation being pervious and the drilling fluid thus being under a relatively high pressure head at the level in the bore hole adjacent the producing formation, a penetration and substantial infiltration of the aqueous phase of the drilling, fluid to the formation generally occurs. Connate water may also be present in the producing formation together with the oil and gas therein prior to the drilling operations.

Whatever the origin of the water in the producing zone may be, it is found that its presence therein seriously impairs the subsequent productivity of the well, particularly in low pressure zones. Since it apparently has a higher adhesive tension than oil for the surface of the sand particles in the productive zone, the water apparently partially displaces the oil film from the sand grains and capillaries. In any event, whatever is the actual physical state of the water in the producing formation, its presence in the producing formation actually greatly reduces the effective porosity and permeability of such for- It is accordingly an object of this invention to provide a treatment for removing water from the oil or gas-producing formations immediately surrounding the well bore hole and thus to increase the effective permeability of such formations and the productivity of the well.

It has been discovered that the removal of water from the producing sands can be effectively accomplished by subjecting them to the washing action of so-called soluble oils which are capable of lowering the surface tension forces holding the a water in the sands and of dissolving or emulsifying the water.

The wash oils which have been found suitable for removing water from producing formations are in general the so-called soluble oils having the ability to disperse spontaneously in water and-under some conditions the property of apparently dissolving both the oil without visual occurrence of two phases. It is probable that such oils form emulsions with the Water which in some cases where the refractive indices of the oil and water phases are substantially equal which cannot be distinguished from a homogeneous solution by ordinary visual inspection. However, when an excess of water is taken up with the soluble oil, it finally assumes the appearance of an emulsion but the dispersed particles are found to be exceedingly small and readily able to pass through the small capillaries, such as occur in permeable oil-producing formations.

Soluble oils which have been found to be suitable are in general the sulfonated mineral and vegetable oils and the water-soluble salts thereof.

For example, sulfonated castor oil ond sulfonated olive oil have been effective. A sulfonated mineral oil, such as that produced as a by-product by the heavy acid treatment of a petroleum fraction to give what is known as a white oil, and the sodium or potassium salts of such sulfonated oil has been found to be effective.

A compounded soluble oil containing thefbefore mentioned sulfonated mineral oil which has been found to be particularly suitable for treating wells to increase the effective permeability of the surrounding oil-producing formation com.- rises a mixture of the following materials:

I Pei cent by weight A sulfonated petroleum fraction, such as PB emulsifier manufactured by Sonneborn and Sons (sodium and/or potassium salt of sulfonated petroleum fraction) 16.1 Potassium corn oil soap .l 8.1 Diethylene glycol 3.2 Methyl Carbitol '32 Rosin 3.2 Water 4.8, Light naphthenic lubricating oil fraction (approximately 100 sec. S. U. at 100 F.) 61.4

Total mac Other soluble oils made with other emulsifiers which are useful as wash oils are as follows:

Per cent" Potassium nap 15.0 A high naphtllenic lubricating oil fraction having a viscosity oi approximately 100 sec. S. U. at 100 F 85.0

min

Aerosol (an ester of a sulfonated bicarboxylic acid produced by the method disclosed in U. S. Patent #2,02B,d9l)

A light naphthenic lubricating oil fraction, such as kerosene or distillates having a viscosity of approximately 45 sec. S. U.

Naphthenio petroleum fraction having a viscosity of approximately 45 sec. S. U. at 100 F d 57 Other materials which in themselves have been found suitable for treating the productive sands are sulfonated fatty oils and acids and water soluble salts thereof, sulfonated mineral oil and water soluble salts thereof. Examples of sulfonated fatty oils are sulionated easier and sulfonated. olive oil. An example of a sulfonated mineral oil is that produced as a sultonated byproduct of "white 0 manufacture, resulting from a heavy sulfuric acid treatment of a parafi'in petroleum fraction which may have a viscosity ranging from approximately 50 sec. to 40d sec. Saybolt Universal at 100 F.

In practice, the treatment of penetrated oil or gas productive sands with the soluble wash oil is preferably made after the drilling of the well has been completed although in some cases the material may be added to the drilling fluid during the drilling operation through the oilproducing sands. when the treatment is performed, on a completed well ready for production, the soluble oil is introduced into the well in a body and allowed to flow by gravity to the s penetrated oil sands or to be circulated to the said sands with the drilling fluid under pressure. Under the latter method it is desirable to employ slidable plugs or division dams at the interface between theintroduced wash oil and the mud 10 which may pass down through the casing upon circulation of the said drilling mud in a manner similar to that employed in the conventional method of cementing wells. It may be desirable to impress additional gas or oil fluid pressure upon the liquid in the well to force the wash 1 oil into the producing formation to be treated. The wash oil having been circulated to the producing formation, the pressure on the fluid contents of the well containing the wash oil may gothen be varied to cause the oil to alternately penetrate the formation and to return from the formation to the well bore thereby more effectively scrubbing the sands surrounding the well bore hole and thereby at the same time carrying the dissolved water with the returning wash oil to the said well bore hole from which it may subsequently be removed. The balance of the soluble wash oil remaining in the treated formation surrounding thebore hole together with its content of dissolved water from the said formation is subsequently removed by the flow of the oil upon production of the well.

The quantity of liquid to be employed for the treating operation will, of course, vary with each 3g well, depending primarily on the diameter of the bore hole at the bottom of the well and on the thickness of penetration of the oil-producing sands, In general, however, a suflicient amount of the wash liquid is introduced into the well to force the liquid approximately four or five feet into the surrounding formation by the hydrostatic head of the combined fluid in the bore hole. As stated hereinabove, a desirable method of eifecting the penetration of the wash oil into the producing'fotion the required distance, is to introduce the repuired amount of the wash material into the well and then place it under a superimposed pressure for a sufficient time to cause the material to penetrate into the formation and dissolve the water contained in it. The

necessary pressure to force the material into the formation may be supplied by forcing a gas, such as air or fixed hydrocarbon, into the well until a sufiioient pressure is provided therein. After the material has been maintained at the producing zone under the superimposed gas pressure for a suincient period of time, say twelve to twenty-four hours, the pressure may be released ,to atmospheric and the liquids in the well pumped or bailed out. If desired, the application of the pressure on the formation in this manner may be carried out intermittently, that is, the material introduced into the well may be maintained under pressure for a shorter period of time, say for one hour, and then the pres sure released for a corresponding period of time to allow the dissolved material or emulsified water to flow back. into the well. The pressure is then reapplied to the formation for another period of time and then'again released and so on until the proper treatment of the producing formation has been accomplished.

In some cases it may be necessary to repeat the above operations one or more times using 75 fresh liquid for each operation in order to obtain ployed in any one operation may be contaminatedv with a suilicient amount of connate water or other dissolved substances before it has been able to penetrate a sumcient distance in the oil-=producing sands to accomplish the desired reduction and eiiective permeability thereof.

While the application of our invention is particularly suited to low producing wells inflow pressure formations which have been in operation for a considerable period of time, the invention is equally well adapted to the treatment of new wells. In the treatment of new wells, however, which are initially large producers of oil or gas, it may be preferable to first bring the well into production and to allow the well to continue to produce until the oil production rate is materially reduced before the treatment to remove the connate and other water in the formotion is made.

suiionated mineral oil, and sulfonated vegetable oil, forcing the wash liquid into the interstices of the iormation to contact water absorbedtherein, subsequently withdrawing said wash liquid together with said water from the formation and subsequently producing the well.-

' 2. A method according to claim 1 in which the wash liquid is a sulfonated mineral oil.

3. A method according to claim 1 in which the wash liquid is a suifonated vegetable oil.

4. A method eccordingto claim 1 in which the wash liquid is a. mixture of a sulfonated oil and a light naphthenic mineral oil fraction.

5 A method of increasing the production of an oil or gas well comprising introducing into the well a soluble oil econsisting of a mixture of approximately 15.1% of a. sulionated petroleum fraction, 8.1% potassium corn oil soap, 2.3% di- The above description of our invention is not to be taken as limitingsince many variations may be made by those skilled in the art within the scope of the following claims.

We claim: 1. A method of increasing the production of an oil or gas well comprising introducing into the well a wash liquid of the class consisting of ethylene. glycol. 3.2%, methyl Carbitol. 3.2% rosin, 4.8% water and 61.4% of a light naphthenic lubricating oil fraction, the said percentage being by weight forcing said mixture into the interstices of the formation to contact water adsorbed'therein. withdrawin said mixture together with N w ijrcmjthe formation and subsequently producing well.

PHILIPI-L JONES.

MARCELLUB T. PLAN/IAN.

CERTIFICATE OF CORRECTION.

Patent No. 2,5L 2r,106. February 22, 19th.

PHILIP H. JONES, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 18, claim 5, for "2.5%" read --5.2%-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of January, A. D. 1915.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 2,5L 2,106-. February 22, 191 14,.

PHILIP H. JONES, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5 second column, line 18, claim 5, for "2.5%" read -5 .2%-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 16th day of January, A. D. 19h5.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

